Square, founded by the creator of Twitter, lets people accept credit cards with their smart phones. That innovation could transform transactions in surprising ways. [This article is from the March issue of Technology Review, which will be available online on February 22nd.]

What matters for commuters is not just if the train will be on time, but how long the journey will take. It's an important factor in public transportation and can make the difference in helping commuters choose mass transit over more polluting and costly transport like cars or airplanes.